Consider the formulation of the County Hospital emergency room problem as a preemptive priority queueing system, as presented in Sec. 17.8. Suppose that the following inputted costs are assigned to making patients wait (excluding treatment time): $10 per hour for stable cases, $1,000 per hour for serious cases, and $100,000 per hour for critical cases. The cost associated with having an additional doctor on duty would be $40 per hour. Referring to Table 17.3, determine on an expected-total-cost basis whether there should be one or two doctors on duty.